1. Field of the Invention
The present invention relates to a brake disc in which a disc plate and a hat part are made of different materials and are mechanically coupled to each other by rivets.
2. Description of the Related Art
Because of the shortage of oil and climate changes, worldwide automobile manufacturers have worked hard to develop techniques to enhance fuel efficiency. In particular, techniques for reducing the weight of a vehicle without lowering the performance have recently attracted attention. More specifically, a reduction in the weight of a lower portion of a vehicle directly affects an increase in the performance and fuel efficiency of the vehicle. Further, reducing the unsprung mass, which directly pertains to a wheel drive load, effectively enhances the fuel efficiency.
Among such technology, the techniques for reducing the weight associated with brake discs, which takes up a large portion of the unsprung mass, have been popular among automotive manufacturing companies. Particularly, the use of a combination of aluminum and grey cast iron to reduce the weight of the brake disc without lowering its performance.
As shown in FIG. 1, a conventional brake disc 10 includes a hat part 30 which is mounted to a hub, and a disc plate 20 which generates friction when braking. The hat part 20 and the disc plate 20 are typically made of grey cast iron which contains flake graphite and have superior braking characteristics, for example, superiority in vibration damping capacity, damping ability, heat resistance and a lubrication function.
However, because the specific gravity of grey cast iron is 7.2 g/cm3, the brake disc is comparatively heavy, resulting in a reduction of fuel efficiency. Therefore, to mitigate this problem, it would be beneficial to develop a brake disc using different materials including grey cast iron and aluminum. Further, a disc structure which can reliably mechanically couple the two elements made of the different materials to each other to satisfy the desired performance, for example, in durability, heat resistance, distortion resistance, etc., would be beneficial in further reducing the overall weight of the vehicle.
It is to be understood that the foregoing description is provided to merely aid the understanding of the present invention, and does not mean that the present invention falls under the purview of the related art which was already known to those skilled in the art.